Generally in religion Islam every follower is called a Muslim and a true follower is called a Moomin

However in Spiritual Islam and during the Golden Islamic Era only a true follower is called a Muslim

A true follower who is fully submissive to the Will of God
is called a Muslim

Not submissive to the commands

Commands includes pronouncement of shahada and fundamental guidelines

Commands and fundamental guidelines are constituted only in the man made altered hadith, man made for his convenience

Not in the Quran, the word of God / Law of Nature

Commands and fundamental guidelines are made obligatory in religion Islam as a discipline to reach

RIGHTEOUSNESS and CONSCIOUSNESS

It is a means to reach

RIGHTEOUSNESS and CONSCIOUSNESS

But majority of Islam followers has misinterpreted that disciplines such as shahada, following five pillars, sharia and sunnah are Islam

However in spiritual Islam

A person who has gained internal peace is called a Muslim

A man who does not harm anybody is called a Muslim

A Muslim is a person who does not divide 

The spiritual truth is

A follower by reciting kalima shahada does not become a true follower

But

Every true follower SHALL recite the Kalima as a discipline

In spiritual Islam a shallow follower cannot be given a title or give him a label or a name as Muslim

What is the Will of God or what is the guidance to achieve this internal peace ?

How gently he lived

How he loved his fellowmen amid failures and disappointments without attachment

How peace and harmony he spread

How humbly he accepted whatever meant for him without complain

How gracefully he let go things not meant for him without a protest

How truthful and sincere his dealings

How modest his attitude

How peaceful his behaviour

How content his desires

How sensitive he is against injustice

How selfless his character

How simple his attire

How he dislike recognition and efface achievements to suppress his ego

All others are nothing but the foolishness of the human ego

This man who is called a Muslim can be born in any tribe, any nation, any religion, without a religion, bearing any name, wearing any costume, eating any food of his choice, chanting any mantrams and performing any rituals

If any human exercise his conduct in attributes of humanity

If any human exercise his conduct in righteousness and consciousness

He is unconsciously a Muslim and he is involuntarily in Islam before the eyes of God (Allah)

In other words He himself doesnt know that he is a Muslim and he is in Islam

Only a wise with a liberal mindset, with rational thinking can understand the diversity, independent and impartiality of God (Allah) who is called the Law of Nature